I want to try to automate my water changes as much as possible. I've been doing them the hard way.

Here's a little bit of a plan I have. If you could make suggestions or tell me if things would work that would rock.

1: Get two 18g rubbermaid totes. One will hold RO/DI water, the other will hold RO/DI water for me to mix salt in. Ideally these would be connected to sensors or floats that have them automatically fill up and stop when a certain level is reached. I don't know what I am looking for to make this possible. But I do know I will need an RO/DI system that has an on/off that can be triggered by sensors or floats?

2: Put a small pump inside of my aquarium or sump. This will be connected to a switch so that I can turn it on to drain and turn it off to stop draining. I would drain into the bathtub drain line plumbing (luckily, this is directly behind the aquarium).

3: After the salt in the salt mixing container has mixed and I have drained some water.. have a pump in that container pump water from the salt container into the tank. Again, I would like to have this on a switch so that I can start it and stop it manually. When I'm done, the sensor/float will detect that water is missing and fill it back up with fresh RO/DI ready for salt to be mixed in it again.

4: Put a sensor/float in my sump to have the water reservoir water pumped in for automatic topoffs.

So my questions are

Your thoughts?
What are these sensor/float thingies I'm talking about.. I know they are around and can be done.
What are the switches called that I'm looking for that will allow me to turn on/off?
How can I get two containers to fill up automatically using one RO/DI system?

autotopoff.com sells float switches that can control anything electrically for a good price. That would work well for the top off.

For the RODI system, you can install float valves to shut off the "good" water, and a auto shut off valve that will also shut off the waste water line (you need both or the waste water will just keep on running).

I have a similar system to what you are talking about set up, but I put my containers up high so I can just gravity feed to the sump for PWCs and to the ATO container for top offs. Do you already have an ATO container setup?

Here is how mine is setup:

Containers are 12 gal water containers, and I installed bulkheads on the bottom with hose barbs.

Each tank has 2 holes I drilled in the top sides: 1 for the float valve that shuts off the RODI system, and the other is just a bulkhead with a hose that goes to the drain, installed above the float valve, in case of failure (so the water will just run to the drain in the event of a shutoff failure, instead of on the floor).

I spray painted it black to match my speakers and aquarium cabinet, so you can hardly tell its back there. Since I painted it black it is impossible to tell how much water is left, so I added a float gauge to tell me how much water is left and tell me when full during filling.

All in all, it takes me about 10 minutes to unwind the 30' hose, fill the ATO container, pull 10 gallons out via a few buckets and a siphon, and run SW back into the tank for replacement. All the RODI stuff in the laundry turns off automatically so dont have to watch it too close. I just turn it on at night and turn it off the next night. I just have a 3 way valve to determine which tank will fill.

Question.. you have a container of top off water, leading to another container that holds top off water. How come? Why not just tube your first container to the sump?

Your setup is might impressive. But, I'm looking for something even easier. Here's how I would like it to work.

Flip switch to drain water - flip it back to stop draining.
Flip switch to fill with new SW - flip it back to stop filling.
Both containers get auto-filled with new water for my next water change.
First container tops off the sump.

My current setup is manually turn on ro/di, fill 18g tote, turn it off. Mix salt with heater/pump for a day. Drag the tote beside the aquarium. Use a gravel cleaner to siphon out water into another 18g tote. Drag that tote to the bathtub and use the gravel cleaner to siphon it down the bathtub drain. Use a gallon pitcher to refill aquarium with new SW. Store the extra tote, refill the SW tote with RO/DI water.

The whole thing only takes like a half an hour. It's not really that much work, but I would like to enjoy water changes and look forward to them. I've been doing it this way every week for over a year.

I'm determined to have it done with the flip of a few switches.. just need to think harder lol

Each of those float switches would power a solenoid valve placed after the split in the RO/DI line, so when triggered by low water level, the valve would open and allow my RO/DI to fill the containers.AutoTopoff.com

Something like this:

A few problems/questions (i am new to float switches and solenoid valves)

1) Does this look right?

2) My RO/DI unit is currently controlled by a ball valve. It is on when I open the ball valve and off when I close it. With this setup, I would leave the ball valve open and rely on the solenoid valves to stop the water on the output lines. Would this damage my RO/DI unit?

3) When either solenoid valve is open I'd also need a solenoid valve on the waste water line to open. Can these float switches power two valves?

Looks right. No reason the float switches can't power 2 valves. They do have a max wattage rating but I don't think 2 small solenoids would touch it. It won't hurt your RO system to control it
This way, so looks to me like you are moving in the right direction. As soon as one tan is full the valve closes; other tank continues filling until solenoid is actuated. Looks good to me.

Everything I have read and seen says it is ok. Kind of like having a ball valve on the end of a garden hose. Once it fills to the point of equilibrium with the input pressure it stops building pressure, so I don't see how it would hurt anything. My ball valve/shutoff valve setup turns mine off all the time in a similar fashion while the source valve is still open... And I think a lot of folks have it setup this way.

As an example, my folks have an RO system under their sink that is controlled in a similar fashion (the storage tank cuts off the water flow with a float) and it has been running 20 years.

Interesting. The float shuts off the water with water pressure buildup? I would guess my water pressure is in the range of 60 PSI.

And I just got to thinking.. the first container would be holding topoff water only. Why not just put the float switch in my sump and eliminate the first container all together. It would still be the same diagram, except the first container would be my sump and the second would be a tote.

Talking this out really helps. :P

EDIT| Nvm, I need topoff water for my 10g and QT as well. The container would be the better idea.